The demands for dependable high band width and high speed communications systems increases daily. These demands are no longer simply the need for better vocal communications but also include the need for the high speed transmission of enormous quantities of digital data. As is well known by those skilled in the art, electrical conductive land lines have been inadequate for carrying the communication load for decades, and have been replaced by other high band width transmission techniques. One technique is the use of light to carry high speed data transmission, and such light or optical systems require “optical switches” to assure data transmitted from one location reaches its intended destination. A technique for optical switching is to selectively direct a light beam that is carrying information from one or more first optical fibers accurately and precisely to any selected fiber in a second group of optical fibers. Mirrors that receive a light beam and then reflect the light beam to any selected fiber of a group of fibers upon demand have been particularly effective for such optical switching.
Of course, as will be appreciated by those skilled in the art, unless the received light beam can rapidly be redirected from one fiber to another fiber, many advantages of using light as the transmission medium may be lost. In addition, it is important to keep the power or energy required to switch the light beam as low as possible. The need for the accurate positioning of a light beam onto any selected one of a large number of very small receiving optical fibers has typically required cumbersome, heavy, and relatively massive switching equipment. Of course, the use of such massive switching equipment is at odds with the need for high speed equipment and equipment requiring low energy.
More specifically, referring to FIG. 5A, there is illustrated a prior art two axis optical device 10 having a first pivoting axis 12 and a second pivot axis 14 that is orthogonal to first axis 12. As shown, there is a support structure 16 defining first and second torsional hinges 18a and 18b lying along the first pivotal axis 12. Although shown as a frame that completely surrounds a gimbals member 20, the support structure 16 may instead comprise two support anchors 16a and 16b as shown in FIG. 5A. Also as shown in FIG. 5A, gimbals member 20 is supported by the torsional hinges 18a and 18b and, in turn, includes a second pair of hinges 22a and 22b that lie along the second pivotal axis 14 that is orthogonal to the first pivotal axis 12. Gimbals member 20 further includes a first pair of axial charged permanent magnets 24a and a second pair of axial charged permanent magnets 24b. As shown, these two pairs of permanent magnets 24a and 24b are spaced from the first pivotal axis 12. As will be appreciated, the gimbals member 20 is supported by the first and second torsional hinges 18a and 18b to allow rotation around the first pivotal axis 12. Therefore, the two pairs of magnets 24a and 24b provide considerable inertia with respect to pivotal motion around axis 12.
The pair of torsional hinges 22a and 22b defined by the gimbals member 20 pivotally support an optical portion 26 such as a mirror having a reflective surface 28 as shown, and a back side (not shown). As discussed above, the pair of torsional hinges 22a and 22b that support the optical portion or mirror 26 are aligned along the second pivoting axis 14. Also as shown, the optical portion 26 includes a pair of tabs 30a and 30b each of which supports a pair of permanent magnets 32a and 32b. 
From the figure it is seen that the two pairs of permanent magnets 32a and 32b lie along first axis 12, but are also spaced away from the second pivoting axis 14 about which the optical portion 26 oscillates. Therefore, in the same manner as discussed above with respect to magnets 24a and 24b, there is also significant inertia created by spaced apart permanent magnets 32a and 32b with respect to pivotal motion around the second pivotal axis 14.
Referring now to FIG. 5B, there is shown a first side view of the gimbals member 20 and the optical portion 26 shown in FIG. 5A. Also shown in FIG. 5B are a pair of electromagnetic coils 34a and 34b that interact with the magnets 24a and 24b to create rotation of the gimbals member as shown in the figure. As can be seen from FIG. 5B, one magnet of the pair of magnets 24a is on the top side of the gimbals member and the second magnet of the pair is on the bottom side. This is also true for the other pair of permanent magnets 24b also shown in FIG. 5B. As also was mentioned, the pairs of magnets 24a and 24b are axially charged as shown in FIG. 5B such that the electromagnetic coils 34a and 34b can provide significant drive force to position the gimbals member 20. FIG. 5C is similar to 5B, except it illustrates the interaction of the two pairs of magnets 32a and 32b on the tabs 30a and 30b of the optical device 26 with magnetic coils 35a and 35b. However, as was discussed above, although the structure of FIGS. 5A, 5B, and 5C is balanced, the weight of the two magnet pairs 24a and 24b spaced away from the pivotal axis creates a significant moment of inertia in the structure, which of course requires more energy to drive and is, therefore, inherently slower because of the large moment of inertia.
Referring now to FIGS. 6A and 6B there is shown a second prior art pointing optical structure or mirror having significantly reduced moment of inertia for the pivoting optical portion 26a. However, there is still a significant moment of inertia with respect to the pivoting of the gimbals member 20a around the first pivotal axis 12. Portions of the optical assembly of FIGS. 6A, 6B and 6C that correspond to similar structures from the assembly of FIGS. 5A, 5B, and 5C carry the same reference numbers. As shown, the optical assembly of FIGS. 6A and 6B still includes a support structure 16 that defines first and second torsional hinges 18a and 18b that support a gimbals member 20a. However, instead of being spaced away from the pivotal axis 12, the permanent magnets 36a and 36b for driving gimbals member 20a are located on the back side of gimbals member 20a as indicated by dotted lines. Also, as shown, the magnets 36a and 36b are located on the pivotal axis 12. Further, as shown in FIG. 6B, permanent magnets 36a and 36b are diametrally charged as indicated by the large double headed arrow running parallel to the gimbals surface. This is different than the axially charged permanent magnets 24a and 24b used in the example shown in FIGS. 5A, 5B, and 5C. Gimbals member 20a also defines a pair of torsional hinges 22a and 22b that support the optical portion 26a. However, as shown, drive magnets 38a and 38b used for pivoting the optical portion 26a are located on the pivotal axis 14 and on the back side of the optical portion 26a rather than being spaced away from axis 14 as was the case for the axially charged magnets 32a and 32b shown in FIGS. 5A, 5B, and 5C discussed above. Further, the permanent magnets 38a and 38b used for pivoting optical portion 26a are also diametrally charged rather than axially charged. It will be appreciated that by locating the drive magnet for both the gimbals member 20a and the optical portion 26a on their respective pivoting axis, the moment of inertia of the two structures is reduced.
Further as shown and as mentioned above, the moment of inertia of the pivoting structure is further reduced by mounting a magnet only on the back side of the respective gimbals member 20a and optical portion 26a rather than a pair of magnets, one each on the top side and back side as was done in the prior art example of FIGS. 5A, 5B, and 5C. The use of a single magnet on the underside of the gimbals structure 20a and optical portion 26a may result in these structures being slightly out of balance, but this disadvantage is more than offset by the reduction in the moment of inertia of the structures. FIGS. 6B and 6C provide an illustration of the interaction of the diametrally charged magnets and the electromagnetic coils.
Although the moment of inertia for the individual optical portion structure 26a and the gimbals structure 20a is substantially reduced by placing the drive magnets on the corresponding pivoting axis of the structure, it will be appreciated, however, that the permanent magnets 38a and 38b, used to drive the optical portion 26a, are spaced a significant distance away from the pivotal axis 12 of the gimbals member 20a. Consequently, although the permanent magnets 36a and 36b used to pivot the gimbals structure 20a have been placed on the pivotal axis 12 to reduce the increased moment of inertia, this reduced moment of inertia is offset by the moment of inertia created by the drive magnets 38a and 38b of the optical portion 26a, which have now been spaced away from pivotal axis 12.
Therefore, it would be advantageous to provide an inexpensive, high speed, low inertia, optical device that can accurately and precisely direct a light beam to a selected location or receiving optical fiber.